The present invention relates to metal cleaning equipment and more particularly to a chemical cleaning system wherein scrap metal parts contaminated with oil, grease and other foreign materials are cleaned as an incident of being salvaged for reuse.
A conventional way of cleaning contaminated scrap metal is to incinerate the contaminants and thereafter cool the scrap material by passing it through a cooling chamber wherein it is cooled by water or air. Such incinerating procedure is subject to a number of disadvantages, including air pollution and undesirable oxidation resulting from the wide variations in temperature between burning and cooling. In addition, a substantial quantity of fuel is required to incinerate the combustibles, a typical unit capable of handling 20 tons of scrap per hour requiring 54 million btu to incinerate the contaminants.
It has also been a standard practice to clean contaminated metallic parts by passing them through a drum-type washer wherein they are selectively subjected to various chemical washing and rinsing operations, with or without subsequent drying of the parts, depending upon how and when they are to be recycled. By way of comparison, a drum-type washer capable of processing twenty tons of scrap per hour only consumes about 8,000,000 btu per hour to heat the washing solution, and at the same time does not pollute the air. Furthermore, parts cleaned by a washing operation contain less residue than parts cleaned by incineration, and where the parts are melted for reuse it has been found that washed parts produce from 20 to 25 percent less slag in the melting furnace than do parts cleaned by incineration.
There are, however, a number of disadvantages to present drum-type washers, particularly insofar as fines recovery and sludge removal is concerned. For example, a substantial amount of scrap fines are discharged from the washing drum along with the washing solution, and heretofore the washing solution has been diverted into a tank or trough extending along one side of the drum in which a series of perforated catch baskets are suspended to collect and retain the fines. In normal operation, these baskets must be removed and emptied every few hours. In addition, a portion of the removed contaminants will settle in the bottom of the trough as sludge, and must be removed by dredging at regular intervals.
In contrast to the foregoing, the present invention provides an integrated scrap washing and solution recovery system wherein both the fines and sludge, as well as free oils floating on the surface of the washing solution, are continuously and automatically removed for reuse or ready disposal.